docs(screenshots): #579 teacher analytics + hotspots widget QA evidence

Page rendered against seeded data in the local Code Academy tenant with all
four signals populated (practice, exercise, checkpoint, exam question) and both
label-vs-Elo mismatch directions present. 7d/30d/90d differ because the seed
spreads attempts across three time bands, so the window switcher is shown doing
real work rather than re-rendering the same list.

Widget shots cover the three demo fixtures: default, all-clear, empty.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VqQTE7LDYPx7d15BcWLGfC

Author: guillermoscript